In situ synthesis of silver nanostructures on magnetic Fe3O4@organosilicon microparticles for rapid hydrogenation catalysis

Abstract

A novel protocol to prepare multifunctional magnetic organic–inorganic nanostructured catalysts of Fe₃O₄@organosilicon/Ag with tailored properties is developed. Such nanostructure design endows the catalysts with superparamagnetism (11.6 emu g⁻¹), excellent oxidation resistance, and catalytic activity. Fe₃O₄ nanoparticles (NPs) are encapsulated with porous organosilicon via improved self-assembly of a flexible-bridged organosilicon precursor without templates. Subsequently, dispersed Ag NPs are in situ grown on the porous microparticles via a silver mirror reaction. The as-prepared multifunctional catalysts are characterized by scanning electron microscopy, X-ray photoelectron spectroscopy, a vibration sample magnetometer, X-ray diffraction, thermal gravimetric analysis, and nitrogen adsorption and desorption, respectively. The resultant hybrid microparticles possess micro- and nano-pores, and exhibit a small hysteresis loop and low coercivity. Meaningfully, they exhibit exceptional catalytic performance for the reduction of 4-nitrophenol in the presence of sodium borohydride and could be reused at least 9 times with excellent stability by means of convenient magnetic separation. The catalysts could be employed to reduce other dyes such as methylene blue, orange G and rhodamine B, and their corresponding reductions follow pseudo-first-order reactions. Therefore, the proposed structure design and scalable route for the synthesis of hierarchical catalysts can pave the way for synthesizing other catalyst systems to address the diverse reaction demands.